I managed to do a bit more than 3 kilometres (a bit more than 1.86 miles) on the IMA batery alone. Or almost, as the gas engine kicked in for a couple of seconds to assist on a steep up-slope.
Point is that, the battery was not fully charged (@4/5 -but I do not trust the battery charge vol) at the begining of the video and now that I sit back and think, I could have avoided that 3 second petrol-engine kick in by not being that hard on my gas pedal.
Nevertheless, the drive was mildly down-slope at first, followed by two long flat parts. I also had to overtake a truck somewhere in the middle.
I have to apologise for the poor video quality but it was taken very early in the morning, car facing the rising sun, very poor road asphalt quality.
2 adults as passengers (191 kilos both), tank @ about 1/2, 4.6lit/100 km fuel consumption, no wind, temp 25 degrees Celcius.
YouTube - Honda Insight 3+ km on IMA battery.mp4